class CSS3DObject extends THREE.Object3D {
  constructor(element) {
    super(element);
    this.element = element;
    this.element.style.position = 'absolute';

    this.addEventListener('removed', function() {
      if (this.element.parentNode !== null) {
        this.element.parentNode.removeChild(this.element);
      }
    });
  }
}

THREE.CSS3DObject = CSS3DObject;

THREE.CSS3DSprite = function(element) {
  THREE.CSS3DObject.call(this, element);
};

THREE.CSS3DSprite.prototype = Object.create(THREE.CSS3DObject.prototype);
THREE.CSS3DSprite.prototype.constructor = THREE.CSS3DSprite;

//

THREE.CSS3DRenderer = function() {
  console.log('THREE.CSS3DRenderer', THREE.REVISION);

  var _width, _height;
  var _widthHalf, _heightHalf;

  var matrix = new THREE.Matrix4();

  var cache = {
    camera: { fov: 0, style: '' },
    objects: new WeakMap()
  };

  var domElement = document.createElement('div');
  domElement.style.overflow = 'hidden';

  this.domElement = domElement;

  var cameraElement = document.createElement('div');

  cameraElement.style.WebkitTransformStyle = 'preserve-3d';
  cameraElement.style.transformStyle = 'preserve-3d';

  domElement.appendChild(cameraElement);

  var isIE = /Trident/i.test(navigator.userAgent);

  this.getSize = function() {
    return {
      width: _width,
      height: _height
    };
  };

  this.setSize = function(width, height) {
    _width = width;
    _height = height;
    _widthHalf = _width / 2;
    _heightHalf = _height / 2;

    domElement.style.width = width + 'px';
    domElement.style.height = height + 'px';

    cameraElement.style.width = width + 'px';
    cameraElement.style.height = height + 'px';
  };

  function epsilon(value) {
    return Math.abs(value) < 1e-10 ? 0 : value;
  }

  function getCameraCSSMatrix(matrix) {
    var elements = matrix.elements;

    return (
      'matrix3d(' +
      epsilon(elements[0]) +
      ',' +
      epsilon(-elements[1]) +
      ',' +
      epsilon(elements[2]) +
      ',' +
      epsilon(elements[3]) +
      ',' +
      epsilon(elements[4]) +
      ',' +
      epsilon(-elements[5]) +
      ',' +
      epsilon(elements[6]) +
      ',' +
      epsilon(elements[7]) +
      ',' +
      epsilon(elements[8]) +
      ',' +
      epsilon(-elements[9]) +
      ',' +
      epsilon(elements[10]) +
      ',' +
      epsilon(elements[11]) +
      ',' +
      epsilon(elements[12]) +
      ',' +
      epsilon(-elements[13]) +
      ',' +
      epsilon(elements[14]) +
      ',' +
      epsilon(elements[15]) +
      ')'
    );
  }

  function getObjectCSSMatrix(matrix, cameraCSSMatrix) {
    var elements = matrix.elements;
    var matrix3d =
      'matrix3d(' +
      epsilon(elements[0]) +
      ',' +
      epsilon(elements[1]) +
      ',' +
      epsilon(elements[2]) +
      ',' +
      epsilon(elements[3]) +
      ',' +
      epsilon(-elements[4]) +
      ',' +
      epsilon(-elements[5]) +
      ',' +
      epsilon(-elements[6]) +
      ',' +
      epsilon(-elements[7]) +
      ',' +
      epsilon(elements[8]) +
      ',' +
      epsilon(elements[9]) +
      ',' +
      epsilon(elements[10]) +
      ',' +
      epsilon(elements[11]) +
      ',' +
      epsilon(elements[12]) +
      ',' +
      epsilon(elements[13]) +
      ',' +
      epsilon(elements[14]) +
      ',' +
      epsilon(elements[15]) +
      ')';

    if (isIE) {
      return (
        'translate(-50%,-50%)' +
        'translate(' +
        _widthHalf +
        'px,' +
        _heightHalf +
        'px)' +
        cameraCSSMatrix +
        matrix3d
      );
    }

    return 'translate(-50%,-50%)' + matrix3d;
  }

  function renderObject(object, camera, cameraCSSMatrix) {
    if (typeof object === 'object' && object instanceof THREE.CSS3DObject) {
      var style;

      if (typeof object === 'object' && object instanceof THREE.CSS3DSprite) {
        // http://swiftcoder.wordpress.com/2008/11/25/constructing-a-billboard-matrix/

        matrix.copy(camera.matrixWorldInverse);
        matrix.transpose();
        matrix.copyPosition(object.matrixWorld);
        matrix.scale(object.scale);

        matrix.elements[3] = 0;
        matrix.elements[7] = 0;
        matrix.elements[11] = 0;
        matrix.elements[15] = 1;

        style = getObjectCSSMatrix(matrix, cameraCSSMatrix);
      } else {
        style = getObjectCSSMatrix(object.matrixWorld, cameraCSSMatrix);
      }

      var element = object.element;
      var cachedStyle = cache.objects.get(object);

      if (cachedStyle === undefined || cachedStyle !== style) {
        element.style.WebkitTransform = style;
        element.style.transform = style;

        var objectData = { style: style };

        if (isIE) {
          objectData.distanceToCameraSquared = getDistanceToSquared(
            camera,
            object
          );
        }

        cache.objects.set(object, objectData);
      }

      if (element.parentNode !== cameraElement) {
        cameraElement.appendChild(element);
      }
    }

    for (var i = 0, l = object.children.length; i < l; i++) {
      renderObject(object.children[i], camera, cameraCSSMatrix);
    }
  }

  var getDistanceToSquared = (function() {
    var a = new THREE.Vector3();
    var b = new THREE.Vector3();

    return function(object1, object2) {
      a.setFromMatrixPosition(object1.matrixWorld);
      b.setFromMatrixPosition(object2.matrixWorld);

      return a.distanceToSquared(b);
    };
  })();

  function filterAndFlatten(scene) {
    var result = [];

    scene.traverse(function(object) {
      if (typeof object === 'object' && object instanceof THREE.CSS3DObject)
        result.push(object);
    });

    return result;
  }

  function zOrder(scene) {
    var sorted = filterAndFlatten(scene).sort(function(a, b) {
      var distanceA = cache.objects.get(a).distanceToCameraSquared;
      var distanceB = cache.objects.get(b).distanceToCameraSquared;

      return distanceA - distanceB;
    });

    var zMax = sorted.length;

    for (var i = 0, l = sorted.length; i < l; i++) {
      sorted[i].element.style.zIndex = zMax - i;
    }
  }

  this.render = function(scene, camera) {
    var fov = camera.projectionMatrix.elements[5] * _heightHalf;

    if (cache.camera.fov !== fov) {
      if (camera.isPerspectiveCamera) {
        domElement.style.WebkitPerspective = fov + 'px';
        domElement.style.perspective = fov + 'px';
      }

      cache.camera.fov = fov;
    }

    scene.updateMatrixWorld();

    if (camera.parent === null) camera.updateMatrixWorld();

    var cameraCSSMatrix = camera.isOrthographicCamera
      ? 'scale(' + fov + ')' + getCameraCSSMatrix(camera.matrixWorldInverse)
      : 'translateZ(' +
        fov +
        'px)' +
        getCameraCSSMatrix(camera.matrixWorldInverse);

    var style =
      cameraCSSMatrix + 'translate(' + _widthHalf + 'px,' + _heightHalf + 'px)';

    if (cache.camera.style !== style && !isIE) {
      cameraElement.style.WebkitTransform = style;
      cameraElement.style.transform = style;

      cache.camera.style = style;
    }

    renderObject(scene, camera, cameraCSSMatrix);

    if (isIE) {
      // IE10 and 11 does not support 'preserve-3d'.
      // Thus, z-order in 3D will not work.
      // We have to calc z-order manually and set CSS z-index for IE.
      // FYI: z-index can't handle object intersection
      zOrder(scene);
    }
  };
};
